I have chickens, but I have never seen anything like your rooster's problem. Are the legs tender to the touch or hot? With the added issue of the tumors, I think Deb's solution might be the most humane.

I looked online too, but nothing matches. And, it doesn't seem infectious. He has had this since a chick, when we noticed all the other chicks were walking over him, or sitting on him. That's when we moved him.

There's a lot of things it could be, and none of them are good news. It doesn't seem like it's a good idea to keep him around to suffer and die, and perhaps spread what he has to some other birds. The consequences of keeping him around to die far outnumbers the small amount of discomfort of euthanizing him. IMHO

The above link lists many of the possible diseases.

I am not afraid of an army of lions led by a sheep; I am afraid of an army of sheep led by a lion. - Alexander the Great

Poor baby.. I have had all types of birds and I have never seen anything like that. But, he may have something genetic that just showed up now Or disease .. Either way I would put him down. That looks painful. And he will eat even if he is not feeling well . Animals hide pain well You might be able to call your vet and they can help you with him.

Just please watch the others... I always remember what Spock said.. " The needs of the many far out way the needs of the few or the one "